This invention relates in general to liquid and gas separators and in particular to a new and useful helium II phase separator.
A phase separator for helium II, particularly under zero-gravity conditions, is described, for example, in the Research Report W-79-47, Free University Berlin, by H. D. Denner et al, December 1979. To separate superfluid helium (helium II) from the gaseous phase, the thermo-mechanical effect (fountain effect) is utilized. With two liquid vessels connected to each other through a capillary system, this effect becomes manifest by a rise of the level at the warmer side. This effect can be observed even if gaseous helium is provided at one side of the capillary system. With the temperature of the liquid bath exceeding that of the capillary system at the side of the gas phase, and with suitably selected boundary conditions, the liquid cannot pass, due to the thermo-mechanical effect of the capillary system, since the respective force is opposite to the temperature gradient thus directed from the exit side to the liquid bath. Such a system may therefore be employed as a phase separator for helium II. The low temperature at the exit side is obtained by lowering the pressure, for example by pumping, so that the liquid cools down by evaporation. Under outer space conditions, this is obtained simply by providing a throttling valve in the gas outlet line through which the helium escapes into the outer space (vacuum). A prior art capillary system suitable for producing the thermo-mechanical effect substantially comprises a plug of a tightly wound aluminum foil having a spiral passage opening, which is inserted in a holder of a thermally well-conducting material and connected therethrough to the gas system. With such a plug, however, strictly speaking, not one, but a plurality of slot-like openings is formed which are irregular and extend spirally adjacent to each other. At the same time, the winding must be tight enough to obtain a maximum slot clearance of about 10 micrometers, since otherwise the thermo-mechanical effect does not occur and liquid helium would escape. Passage openings of this kind are not reproducible, so that always a plurality of plugs of this kind must be fabricated and tested for usefulness.
It is further known from the above cited Report that the thermomechanical effects may also be obtained with narrow annular gaps having a width of about 10 micrometers or less. However, tests have shown that while utilizing the thermo-mechanical effect only for phase separation, the rate of flow of helium through a narrow annular gap is relatively low. With rates of helium flow of about 45 mg/sec. typical for outer space tests, an annular gap having a diameter of about 0.8 meters would be needed for a gap width of about 10 micrometers. Such annular gaps can hardly be produced and are unsuitable for application in space vehicles.
In accordance with the invention a helium II phase separator for use with a bath of liquid helium comprises a member which is insertable into the bath and which has a gas takeoff line for taking off a gaseous helium. The device includes an arrangement of cylindrical members which is disposed in the liquid helium so as to define a plurality of substantially equal flow area passageways connected to the gas takeoff line. In one embodiment the passageway is defined by ring-like square plates which have spaces therebetween. The plates and spaces are dimensioned so that they provide uniform passageways which connect to a central area enclosed by the plates and a centrally disposed displacement body which connects to a gas takeoff line. Advantageously the gas takeoff line comprises a coil member engaged around the cylindrical body and the plates which extend through the cylindrical body into the space for the collection of the gases helium at its one end and to an outlet at its opposite end.
The plates and the spaces defined are substantially equal passageways for the flow of the gaseous helium. In the first embodiment and in another embodiment the equal passageways are defined by a cylindrical body having circumferentially spaced V-shaped grooves which are filled by wedge-shaped inserts precisely positioned so as to define substantially uniform gaps between the inserts and the grooves which connect to a takeoff line for gaseous helium.
Accordingly it is an object of the invention to provide an improved device for the phase separation of helium II which includes a member which is insertable into a liquid helium bath and has a plurality of slot-shaped passage gaps arranged to utilize a thermo-mechanical effect and being of substantially identical flow area and provided in a member which is insertable in the bath of liquid helium.
A further object of the invention is to provide a helium II phase separator which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.